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Application to human health: problems in embryonic development

Chromosomal movement during meiosisresults in four haploid gametes with half the number of chromosomes

as the diploid mother cell

Use your noodle: Understanding the role of chromosome movements in meiosis and mitosis.

Introduction: Biological significance

Non-disjunction- the failure of homologous chromsomes to separate

Aneuplody: Down Syndrome

Chromosomal movement during mitosisresults in the formation of two identical daughter cells

ACTIVITY I, II, III - MEIOSIS STRIP SEQUENCE WITH CHROMOSOME DANCE

Learning Goals Students will be able to explain the movement of chromosomes during mitosis, meiosis, and predict the products.

Active learning includes a strip sequence that will direct a visual demonstration of chromosome movement. This will be followed by clicker questions.

Diversity This activity addresses a variety of learning styles, including auditory, visual, kinesthetic and analytical. Students will also work cooperatively.

ACTIVITY 4- Case study of a Down syndrome baby with with multiple abnormalities.

Learning Goal Students will learn to formulate hypotheses, and design models to test their hypotheses using data from a case study.

Active learning Think-pair-share groups will formulate models to explain causes of Down syndrome, and will predict karyotypes consistent with their models.

Diversity This activity includes students that can learn by visual, analytical and interactive styles.

Students by this point will have seena mini-lecture on the following:

- chromosomes, chromosome replication, chromatids, centromeres- homologous chromosomes- diploid, haploid- gametes, zygotes

- chromosome movements in mitosis- the life cycle: 2n n 2n- spindle, poles

- the salient features of meiosis

Before DNA replication

2n

MEIOSIS

Chromosomefrom mother

Chromosomefrom father

After DNA replication

Sisterchromatids

Sisterchromatids

centromere

centromere

MEIOSIS

MEIOSIS

Pairing of homologous chromosomes

MEIOSIS

nn

End of meiosis ITwo cells

MEIOSIS

n n n n

End of meiosis IIFour cells

gametes

• 2n cell completes DNA replication

• Sister chromatids separate

• Homologous chromosomes separate to opposite poles and cells divide

• Homologous chromosomes pair and align in the middle of the cell

• Gametes contain a single set of chromosomes

• Daughter cells contain a single set of chromosomes, each chromosome consists of two sister chromatids

Group Activity: Place the following events in the order they occur in meiosis:

A

B

C

D

E

F

• 2n cell completes DNA replication

• Homologous chromosomes pair and align in the middle of the cell

• Homologous chromosomes separate to opposite poles and cells divide

• Daughter cells contain a single set of chromosomes, each chromosome consists of two sister chromatids

• Sister chromatids separate

• Gametes contain a single set of chromosomes

Group Activity: Place the following events in the order they occur in meiosis:

A

D

C

F

B

E

Acknowledgements

Group 5 Members

University of Alabama Katrina Ramonell Jane Rasco

Louisiana State University Pat DiMario

University of California, Riverside Richard Cardullo Morris Maduro

Stony Brook University Neta Dean Gene Katz

Group Facilitator – Brian Manske

Pool Noodle Facilitator – Sandy Gossens

Fusion of gametes

sperm

egg

+

zygote

2n

MEIOSIS - nondisjunction

n n n-1n+1

Fusion of gametes

sperm

egg

+

zygote

2n+1

(aneuploid)

Fusion of gametes

sperm

egg

+

zygote(aneuploid)

2n-1

Use your noodle: Understanding the role of chromosome movements in meiosis and

mitosis.

1 Developmental delay -- All children with Down syndrome are delayed, although this may not be apparent until the child is beyond infancy. IQ scores range from 20 (severe mental retardation) to 85 (low normal). Overall learning abilities are usually equivalent to a 6 to 8 year old child without Down syndrome.

2 Gastrointestinal abnormalities -- 2 percent to 5 percent of children have complete obstruction of the small bowel known as duodenal atresia. Another 2 percent have poor movement abilities of the colon and / or rectum known as Hirschsprung disease.

3 Hearing loss -- Some degree of hearing loss is present in 40 percent to 75 percent of children with Down syndrome. Malformations may affect either the middle or inner ear structures. Ear infections can be a frequent, often difficult problem to treat.

4 Eye disorders -- 60 percent of children have eye disorders that need monitoring and treatment. Congenital cataracts (loss of transparency of the lens of the eye), glaucoma (increased pressure within the eye), strabismus (cross-eyed) and major refractory errors (far sighted or near sighted) are the common problems.

5 Leukemia -- Leukemia occurs in one of every 150 children with Down Syndrome. This is 20 times higher than the general population.

6 Thyroid disorders -- Low thyroid levels are seen in approximately 5 percent of children with Down syndrome.

Application: A karyotype is a display of condensed chromosomes arranged in pairs.

Before cell division and replication

2n

MITOSIS

Chromosomefrom mother

Chromosomefrom father

alignment

MITOSIS

After replication

MITOSIS

Sisterchromatids

Sisterchromatids

centromere

centromere

segregation

MITOSIS

MITOSIS

Daughter cells

2n 2n